KR100871407B1 - Electroconductive composition and electroconductive film forming method - Google Patents

Abstract

The present invention can be fired at a low temperature not only in an inert atmosphere but also in an atmospheric atmosphere, prevents oxidation of copper particles, exhibits good conductivity, and provides an inexpensive conductive composition, and conduction in an inert atmosphere or an atmosphere using the conductive composition. It is an object to provide a method for forming a film.

A conductive composition comprising copper as a filler, which is composed of a mixture of copper powder having an average particle diameter of 0.3 to 20 µm and fine copper powder having an average particle diameter of 1 to 50 nm, and OH groups such as ethylene glycol and diethylene glycol. And a solvent comprising a polyhydric alcohol having two or more, and an additive comprising a compound having two or more COOH groups and one or more OH groups, such as malic acid or citric acid, and the number of COOH groups equal or more than the number of OH groups.

Description

Conductive composition and conductive film formation method {ELECTROCONDUCTIVE COMPOSITION AND ELECTROCONDUCTIVE FILM FORMING METHOD}

The present invention relates to a conductive composition used for forming conductive films such as various electronic components, and a method for forming a conductive film using the conductive composition.

In various electronic components and the like, a pattern is formed from a conductive composition using techniques such as a screen printing method, and a low resistance thick film conductive circuit is formed by baking at a low temperature. The general method of forming the thick-film conductive circuit is roughly divided into subtractive process and additive process. Among them, the additive method is a process such as simplicity, cost, and environmental load caused by waste. Has an advantage over the subtractive method.

In general, the characteristics required for the conductive composition used in the additive method include easy formation of a conductive circuit, low resistivity of the resulting conductive film, and good adhesion between the conductive film and the substrate. As such a conductive composition, metal particles, such as gold, silver, copper, palladium, and platinum, are used as a conductive filler, and the conductive composition which uses silver as a conductive filler in particular is used a lot. However, the electrically conductive composition using a silver filler has the drawback that migration is easy to generate | occur | produce.

Regarding the suppression of such migration, it is effective to use copper as a filler, and is excellent also in terms of conductive characteristics and cost. As a method of forming a conductive film using copper as a filler, a technique of realizing low-temperature firing using copper particles having an average particle diameter of 100 nm or less has recently attracted particular attention. For example, Japanese Patent Laid-Open No. 2004-256757 or Japanese Patent Laid-Open No. 2004-327229 uses a conductive ink containing copper powder having a particle diameter of 30 nm or less to draw a conductive pattern by an inkjet method, and draw a nitrogen atmosphere. The method of heating to the temperature of 200 degrees C or less in the inside, and forming a electrically conductive circuit is disclosed.

However, in order to form a circuit having a film thickness of several micrometers level by an inkjet method, it is necessary to repeat drawing and baking, and it has the drawback that a process becomes complicated. In addition, although the above-described method makes it possible to use fine particles of copper by addition of a dispersing agent such as citrate such as ammonium citrate or tertiary amine type monomer, and it is possible to obtain conductivity by low-temperature firing, The resistivity of the film does not reach a level that can be sufficiently satisfied as 20 to 50 times the bulk copper.

As a means of improving these drawbacks, Japanese Patent Laid-Open No. 7-320535 discloses a method of forming a thick film conductive circuit having a thickness of several μm or more by using a screen printing method or a dispenser method. According to this method, an organic metal salt is used as a precursor to produce fine metal particles having an average particle diameter of 100 nm or less, and to be a mixture with copper-based particles having an average particle diameter of 0.2 µm or more, thereby complicating the process of repeating drawing and firing. In addition, the resistivity of the bulk copper can be obtained at less than twice the bulk copper.

In this method, however, it is necessary to use organic metal salts such as carboxylate salts as precursors, and to form fine particles having an average particle diameter of 100 nm or less by heating once. In addition, since the firing conditions of the conductive composition are very high at about 900 ° C. in a nitrogen atmosphere, and the sintering start temperature is also high at about 400 ° C., it is not applicable to, for example, a polymer substrate, and the circuit has a high heat resistance temperature such as a ceramic substrate. It has a drawback that it is limited to uses such as forming a film.

In addition, Japanese Patent Publication No. 2004-534362 discloses a technique for lowering the firing temperature, in which fine copper particles having an average particle diameter of less than 0.3 µm, copper particles having an average particle diameter of 0.3 µm or more, and metal copper are further precipitated by thermal decomposition. A method for forming a thick film conductive circuit is disclosed by a composition composed of an organic decomposable copper compound or a reactive compound such as carboxylic acid capable of producing an organic decomposable copper compound. Moreover, it is also disclosed that the particle | grains of 0.3 micrometer or more of average particle diameters are made into the mixture of particle | grains which have another average particle diameter. According to this method, the organic-decomposable copper compound decomposes during heating to generate copper particles, and it is possible to realize about three times lower resistance of bulk copper by firing at 330 ° C.

However, in the above method, a special mixed gas such as nitrogen-vapor-hydrogen is required as the firing atmosphere, and there is a problem in safety and economy. In addition, since the firing temperature is as high as 330 ° C, it is difficult to apply to a polymer substrate such as a polyimide substrate having a heat resistance temperature of 300 ° C or lower, for example, and in order to be easily applied to a polymer substrate, it has been required to be baked at a lower temperature. .

As described above, the conductive composition containing copper as a filler has a problem in that copper is inherently deteriorated by oxidation, a high temperature is required for firing, and the like. It is not reaching. For this reason, it is easy to form a conductive circuit, and the resistivity of the resulting conductive film is low, about 5 μΩ · cm or less, which is about three times that of bulk copper, and has good adhesion to the substrate without any limitation on the substrate, and inexpensive conductivity. A composition is required.

By the way, there is a demand to obtain a low resistance conductive circuit using a conductive composition made of copper as described above, and can be fired in an industrially easy atmospheric atmosphere, and has a resistance value within a range acceptable as an electronic component, There is also a need for a conductive composition capable of obtaining a conductive film on the order of 100 μΩcm, which is about 60 times higher than that of bulk copper.

That is, since copper deteriorates severely by oxidation, it is indispensable to perform baking in an inert atmosphere or a reducing atmosphere, and therefore the application range is limited in the present situation. Thus, if a conductive composition capable of forming a conductive film having a resistivity in an acceptable range to some extent even by firing in an air atmosphere is provided, the conventional inert atmosphere or reduction for many applications in the range without problems with respect to the resistance value is provided. It becomes possible to replace the conductive composition which requires baking in an atmosphere.

[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2004-256757

[Patent Document 2] Japanese Patent Application Laid-Open No. 2004-327229

[Patent Document 3] Japanese Patent Application Laid-Open No. 7-320535

[Patent Document 4] Japanese Patent Publication No. 2004-534362

In view of the above-described circumstances of the prior art, the present invention can be fired at a low temperature not only in an inert atmosphere but also in an atmospheric atmosphere without undergoing a complicated process, and can prevent oxidation of copper particles as a filler, and provides good conductivity. It is an object of the present invention to provide a conductive composition which is inexpensive and inexpensive, and a method of forming a conductive film in an inert atmosphere or an air atmosphere using the conductive composition.

The inventors of the present application have conducted intensive studies to solve the above-described problems, and by adjusting the solvent and the additive while combining copper particles having different average particle diameters, the conductive composition has a high antioxidant resistance at firing of 200 ° C. or lower in an air atmosphere. The effect was found, and furthermore, it was found that exhibiting good conductivity comparable to bulk copper by firing at 300 ° C. or lower in an inert atmosphere, thus completing the present invention.

That is, the electrically conductive composition which concerns on this invention is a electrically conductive composition containing a metal powder, a solvent, and an additive, Comprising: The said metal powder is a copper powder with an average particle diameter of 0.3-20 micrometers, and fine copper with an average particle diameter of 1-50 nm. It is a mixture of powder, The said solvent is a polyhydric alcohol which has 2 or more OH groups, The said additive is a compound which has 2 or more COOH groups and 1 or more OH groups, and the number of COOH groups is the same or more than the number of OH groups. It is characterized by.

In the conductive composition of the present invention, the metal powder is preferably a mixture in which the fine copper powder is in a ratio of 1 to 100 parts by weight with respect to 100 parts by weight of the copper powder. In addition, the solvent is preferably mixed at a ratio of 5 to 35 parts by weight with respect to 100 parts by weight of the metal powder. In addition, the additive is preferably mixed in a ratio of 1 to 15 parts by weight with respect to 100 parts by weight of the metal powder.

In the electroconductive composition of the said invention, it is preferable that the said solvent consists of at least 1 sort (s) chosen from ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and glycerin. Moreover, it is preferable that the said additive consists of at least 1 sort (s) chosen from malic acid, citric acid, and tartaric acid.

The present invention further provides a method for forming a conductive film, using any one of the conductive compositions of the present invention described above, and applying the conductive composition onto a substrate for heat treatment. Specifically, the method of forming a conductive film characterized by heating and baking at a temperature of 200 to 300 ° C. in an inert atmosphere, or the method of forming a conductive film characterized by heating and baking at a temperature of 150 to 200 ° C. in an air atmosphere. will be.

In the electrically conductive composition of this invention, as a metal powder which is a electrically conductive filler, the copper powder of 0.3-20 micrometers of average particle diameters, and the fine copper powder of 1-50 nm of average particle diameters are used together. When the average particle diameter of the copper powder is less than 0.3 µm, the voids after firing increase, so that a conductive film having a low resistivity cannot be obtained. On the contrary, when the average particle diameter exceeds 20 µm, formation of a fine pattern becomes difficult. In addition, when the average particle diameter of the fine copper powder is less than 1 nm, the aggregation of the particles is severe, so that dispersion in the composition becomes difficult. On the contrary, when the average particle diameter exceeds 50 nm, the contact effect with the copper powder becomes insufficient, and No effect will be obtained.

The mixing ratio of the copper powder having an average particle diameter of 0.3 to 20 µm and the fine copper powder having an average particle diameter of 1 to 50 nm is preferably in the range of 1 to 100 parts by weight of the fine copper powder with respect to 100 parts by weight of the copper powder. If the mixing ratio of the fine copper powder to 100 parts by weight of the copper powder is less than 1 part by weight, the contact effect with the copper powder will not be sufficient, and if it exceeds 100 parts by weight, deterioration due to oxidation will be severe in the air atmosphere. It is not preferable because the resistivity of the conductive film is increased.

As the conductive composition of the present invention, a polyhydric alcohol having two or more OH groups is used as a solvent for dispersing the metal powder composed of the copper powder and the fine copper powder, and at least two COOH groups and one or more OH groups are used as an additive. In addition, the compound whose number of COOH groups is the same or more than the number of OH groups is used. This additive exhibits adsorption on the surface of the metal powder by the OH group, and the oxide formed on the surface of the copper powder is dissolved by the action of the COOH group contained therein, resulting in a surface state exhibiting good conductivity. In addition, some copper carboxylate formed at this time adsorb | sucks on the metal powder surface, and maintains the state which shows favorable electroconductivity.

In addition, with respect to the additive, a compound having two or more COOH groups and one or more OH groups, and the number of COOH groups equal to or more than the number of OH groups is adsorbed on the surface of the metal powder when added in a salt state such as an ammonium salt. However, since the effect of dissolving the oxide on the surface is inferior, sufficient conductivity cannot be obtained. Therefore, it is important that the compound is not added as a salt but as an acid having two or more COOH groups.

In addition, the additive has a function of curing the composition by heating. That is, a compound having two or more COOH groups and one or more OH groups, and the number of COOH groups equal to or more than the number of OH groups is added in part as a solvent by heating and baking at a relatively low temperature during the formation of the conductive film. The polymer is polymerized with a polyhydric alcohol having two or more OH groups, and a polymer is formed to cure the composition.

By the formation of this polymer, a conductive film having sufficient strength and good adhesion to the substrate is formed. Moreover, in the obtained electrically conductive film, the contact | adhesion of metal powders is fully performed by the adhesive effect of a polymer, and the effect which significantly reduces a resistivity is expressed with the favorable surface state mentioned above. Moreover, since the formed polymer suppresses the ingress of oxygen, the oxidation of the metal powder in a conductive film is suppressed. These effects are particularly effective for fine copper powder having an average particle diameter of 50 nm or less having a high surface activity, and the fine copper powder having a surface without an oxide layer promotes strong contact between large copper powders and has excellent conductivity. Expresses properties.

On the other hand, when the temperature at the time of heat baking is higher, for example, when baking at 200 degreeC or more in inert atmosphere, the sintering of fine copper powders or the sintering of fine copper powder and copper powder in the state in which the said antioxidant inhibitory effect was maintained. This progresses and more excellent conductive characteristics are expressed. That is, in the process of temperature rise, a part of the polymer formed at a low temperature is decomposed, and precipitation of metal copper occurs simultaneously by decomposition of copper carboxylate on the surface of the metal powder and the contact portion thereof, Sintering is realized and shows excellent conductivity. In addition, since a part of the polymer remains on the substrate surface and acts as a firm binder between the substrate and the conductive film, very high substrate adhesion is maintained.

The additive used in the present invention can be used without limitation as long as the compound has two or more COOH groups and one or more OH groups, and the number of COOH groups is the same or more than the number of OH groups. However, the additive is preferably high in solubility in a solvent, and therefore, malic acid, citric acid and tartaric acid are preferred, and malic acid and citric acid are more preferred. In addition, as an additive, any 1 type, or 2 or more types of these compounds may be selected, and may be added and mixed to an electrically conductive composition.

1-15 weight part is preferable with respect to 100 weight part of metal powders, and, as for the composition ratio of the additive in a conductive composition, 5-10 weight part is more preferable. When the composition ratio of the additive is less than 1 part by weight, not only the polymer is formed by polymerization with the solvent but also the oxide removal effect on the surface of the copper powder cannot be sufficiently obtained. Moreover, when the composition ratio of an additive exceeds 15 weight part, since the viscosity of a composition becomes high significantly, handling becomes difficult.

The solvent used by this invention should just be a polyhydric alcohol which has two or more OH groups, and can superpose | polymerize with the said additive by heating, and can form a polymer. However, in order for a conductive film to show favorable electroconductivity, it is preferable to evaporate excess solvent at low temperature. Taking these points into consideration, it is preferable to use, for example, one or two or more of ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and glycerin, and ethylene glycol is particularly preferable.

5-35 weight part is preferable with respect to 100 weight part of metal powder, and, as for the composition ratio in the electrically conductive composition of the said solvent, 10-25 weight part is more preferable. If the composition ratio of the solvent is less than 5 parts by weight, the formation of the polymer will not be sufficiently performed, and the viscosity of the composition will increase markedly, making handling difficult. Moreover, when the composition ratio of a solvent exceeds 35 weight part, since a solvent remains excessively in the electrically conductive film after baking, not only will it become high in resistivity, but the intensity | strength of a electrically conductive film will fall, and a pattern cannot be maintained.

A polar solvent can be mixed with the electrically conductive composition of this invention according to the use etc. As a polar solvent in that case, water, alcohol, such as methanol and ethanol, and carbitol are preferable, and 1 type or 2 or more types can be used among these. Moreover, in the electroconductive composition of this invention, the composition and a structure can be selected according to the film thickness, electroconductivity, baking conditions, etc. of the target electrically conductive film.

For example, when forming a conductive film by baking at 200 degrees C or less in air | atmosphere, it is preferable to enlarge the particle diameter of a copper powder, suppressing the ratio of a fine copper powder in order to suppress degradation by oxidation to the minimum. On the other hand, when it is desired to obtain a low resistivity conductive film by firing in an inert atmosphere, it is preferable to make the particle diameter of the copper powder large and to make the particle diameter of the fine copper powder fine depending on the thickness of the conductive film. . At this time, it is effective to mix and use the particle | grains which have a different average particle diameter also about copper powder of 0.3 micrometer or more in order to raise the filling rate of the copper particle in a conductive film.

After the conductive composition of the present invention described above is applied onto a substrate, the conductive film can be formed by heat treatment in an inert atmosphere or in an atmospheric atmosphere. In heat-firing in an inert atmosphere, 200-300 degreeC is preferable and 250-300 degreeC is more preferable. When fired at a temperature exceeding 300 ° C. in an inert atmosphere, there is no problem in particular for the conductive film, but a polymer substrate inferior in heat resistance cannot be used as the substrate. Moreover, since the resistivity of the electrically conductive film after baking does not fully fall in baking temperature below 200 degreeC, it is unpreferable.

Moreover, it is preferable that the electrically conductive composition of this invention is heat-baked at the temperature of 150-200 degreeC in air | atmosphere. When baking by heating to the temperature exceeding 200 degreeC in air | atmosphere, deterioration by the oxidation of a metal powder becomes severe, and the resistivity of the electrically conductive film obtained rises. Moreover, when the baking temperature in air | atmosphere is less than 150 degreeC, since the resistivity of a conductive film does not fully fall but the intensity | strength of a conductive film falls, it is unpreferable.

In the inert atmosphere described above, the conductive film obtained by firing at 200 to 300 ° C. can obtain resistivity of 10 μΩ · cm or less, which is about 6 times that of bulk copper, and 5 μΩ, which is about 3 times that of bulk copper, if conditions are properly designed. Lower resistivity below cm can be obtained. In the case of firing at 200 ° C. or lower in an air atmosphere, a conductive film having a resistivity of about 100 μΩ · cm, which is about 60 times that of bulk copper, can be formed.

Example 1

20 parts by weight of fine copper powder having an average particle diameter of 50 nm produced by a wet reduction method was mixed with 80 parts by weight of a copper powder having an average particle diameter of 0.4 µm (Sumitomo Metallic Mine Co., Ltd., UCP030). It was. After adding 19 weight part of ethylene glycol as a solvent, and 6 weight part of citric acid as an additive with respect to 100 weight part of this mixed copper powder, a high speed planetary motion defoaming kneading apparatus (NBK-1 make). By mixing, the conductive composition of Sample 1 was adjusted.

The conductive composition of Sample 1 thus obtained was applied on a slide glass substrate using a metal squeegee to form a film thickness of about 20 μm to form a pattern of 12 × 40 mm, and then baked at 300 ° C. for 1 hour in a nitrogen atmosphere to form a conductive film. .

About the obtained conductive film of Sample 1, sheet resistance value was measured by the 4-stage immersion method using a low resistivity meter (Mitsubishi Chemical Corporation, Loresta-GP MCP-T600), and a surface roughness shape measuring instrument [ The film thickness was measured by Tokyo Precision Co., Ltd. product, SURFCOM 130A], and volume resistivity was computed. As a result, the volume resistivity of the conductive film of Sample 1 was 3.44 µΩ · cm.

Moreover, the adhesive strength with respect to the board | substrate of the conductive film was investigated with respect to the electrically conductive film of the sample 1 by the X-cut tape method prescribed | regulated to JISK5400. As a result, it was confirmed that the conductive film was not peeled off by the tape (corresponding to 10 points of JIS evaluation scores) and was in close contact with the glass substrate.

Example 2

In the said Example 1, 90 weight part of copper powders with an average particle diameter of 0.4 micrometer, and 10 weight part of fine copper powders with an average particle diameter of 50 nm are mixed, and ethylene glycol 15 is used as a solvent with respect to 100 weight part of this mixed copper powder. Except having mixed 10 weight part of citric acid as a weight part and an additive, it carried out similarly and the conductive film of Sample 2 was formed.

As a result of evaluating the obtained conductive film of Sample 2 in the same manner as in Example 1, the volume resistivity was 3.71 μΩ · cm, and the adhesiveness was 10 points of JIS evaluation scores.

Example 3

In Example 2, although malic acid was used as an additive, it was changed to 6 parts by weight (molar amount as citric acid of Example 2) in consideration of the difference in molecular weight, and the solvent was mixed to match the ratio with the metal powder in the composition. The conductive film of Sample 3 was formed in the same manner except that 19 parts by weight of ethylene glycol was used with respect to 100 parts by weight of copper powder.

As a result of evaluating the obtained conductive film of Sample 3 in the same manner as in Example 1, the volume resistivity was 4.55 μΩ · cm, and the adhesiveness was 10 points of JIS evaluation scores.

Example 4

In Example 2, tartaric acid (L-tartaric acid) was used as an additive, but was changed to 7 parts by weight (molar amount as in citric acid of Example 2) in consideration of the difference in molecular weight, and the ratio with the metal powder in the composition was changed. The conductive film of Sample 4 was formed in the same manner except that the solvent was 18 parts by weight of ethylene glycol based on 100 parts by weight of mixed copper powder.

As a result of evaluating the electrically conductive film of the obtained sample 4 similarly to the said Example 1, volume resistivity was 9.05 micrometer * cm, and adhesiveness was 10 points of JIS evaluation scores.

Comparative Example 1

In Example 2, although lactic acid was used as an additive, it was changed to 4 parts by weight (molar amount as citric acid of Example 2) in consideration of the difference in molecular weight, and the solvent was mixed to match the ratio with the metal powder in the composition. Except having made 21 weight part of ethylene glycol with respect to 100 weight part of copper powders, it carried out similarly and the electrically conductive film of the sample 5 was formed.

As a result of evaluating the electrically conductive film of the obtained sample 5 similarly to the said Example 1, the volume resistivity is 42.2 micrometer * cm, and about adhesiveness, a part of electrically conductive film peeled from the glass substrate with the tape (at two points of JIS evaluation scores). Equivalent).

Comparative Example 2

In Example 2, succinic acid was used as an additive, but was changed to 5 parts by weight (molar amount as citric acid in Example 2) in consideration of the difference in molecular weight, and the solvent was mixed to match the ratio with the metal powder in the composition. The conductive film of Sample 6 was formed in the same manner except that 20 parts by weight of ethylene glycol was used with respect to 100 parts by weight of the copper powder.

As a result of evaluating the electrically conductive film of the obtained sample 6 similarly to the said Example 1, volume resistivity was 181 microohm * cm, and adhesiveness was ten points of JIS evaluation scores similarly to the sample 2 of the said Example 2.

In Example 2, acetic acid was used as an additive, but was changed to 3 parts by weight (molar amount as citric acid in Example 2) in consideration of the difference in molecular weight, and the solvent was mixed to match the ratio with the metal powder in the composition. Except having made 22 weight part of ethylene glycol with respect to 100 weight part of copper powders, the conductive film of the sample 7 was formed similarly.

As a result of evaluating the electrically conductive film of the obtained sample 7 similarly to the said Example 1, the volume resistivity is 110 microohm * cm, and the whole electrically conductive film was peeled from the glass substrate with the tape with respect to adhesiveness (at 0 points of JIS evaluation scores). Equivalent).

[Comparative Example 4]

In Example 2, formic acid was used as an additive, but was changed to 2 parts by weight (molar amount as citric acid of Example 2) in consideration of the difference in molecular weight, and the solvent was mixed to match the ratio with the metal powder in the composition. The conductive film of Sample 8 was formed in the same manner except that 23 parts by weight of ethylene glycol was used with respect to 100 parts by weight of copper powder.

As a result of evaluating the electrically conductive film of the obtained sample 8 similarly to the said Example 1, the volume resistivity was 490 microohm * cm, and the adhesiveness peeled the whole electrically conductive film from a board | substrate with a tape (equivalent to 0 evaluation score). .

The samples 1 to 4 of the above-described examples and the samples 5 to 8 of the comparative examples are shown in Table 1 below, and the evaluation results of the firing conditions of the respective conductive compositions and the obtained conductive films are shown in Table 2 below.

As can be seen from the above results, Samples 1 to 3, which are examples, have a very low resistivity of 5 μΩ · cm or less, which is about three times that of bulk copper, by heating and baking at 300 ° C. for 60 minutes in an inert atmosphere of nitrogen. At the same time, a conductive film having good adhesiveness with the glass substrate could also be obtained. Moreover, although the resistivity was slightly high compared with the samples 1-3, the sample 4 can be said to be sufficiently low resistivity, and adhesiveness with the board | substrate was also favorable.

On the other hand, samples 5 to 8 of the comparative example have the same firing conditions as those of the samples 1 to 4 of the above example, and have two or more COOH groups and one or more OH groups as additives, and the number of COOH groups is equal to or the same as the number of OH groups. Since the above compound is not used, the obtained electrically conductive film had a high resistivity, but also the adhesiveness with the board | substrate was not good except sample 6.

Example 5

10 parts by weight of fine copper powder having an average particle diameter of 50 nm produced by the wet reduction method is mixed with 90 parts by weight of a copper powder having an average particle diameter of 2.8 µm (manufactured by Nippon Atomize Co., Ltd., HXR-Cu), and mixed copper It was made into powder. To 100 parts by weight of this mixed copper powder, 13 parts by weight of ethylene glycol as a solvent and 7 parts by weight of citric acid as an additive were added, and the conductive composition of Sample 9 was adjusted in the same manner as in Example 1.

This electroconductive composition was apply | coated on the slide glass board | substrate by the method similar to the said Example 1, and heat-baking for 30 minutes at 180 degreeC in air | atmosphere in a reflow furnace. As a result of evaluating the electrically conductive film of the obtained sample 9 by the method similar to the said Example 1, volume resistivity was 27.0 microohm * cm, and adhesiveness was 10 points of JIS evaluation scores.

In addition, the conductive composition of the said sample 9 was apply | coated on the slide glass board | substrate by the method similar to the said Example 1, and it heated and baked for 20 minutes at 190 degreeC in air | atmosphere by a reflow furnace. As a result of evaluating the electrically conductive film of the obtained sample 10 by the method similar to the said Example 1, volume resistivity was 29.7 micrometer * cm and adhesiveness was 10 points of JIS evaluation scores.

Example 6

In the said Example 5, it carried out similarly except having changed the copper powder into the flat powder (Cu-HWF-6 of Fukuda Metal Powder Industry Co., Ltd. product) of 6.2 micrometers in average, and made the electrically conductive composition of the sample 11 Adjusted. This electrically conductive composition was apply | coated to the slide glass substrate similarly to the said Example 5, and heated and baked for 30 minutes at 180 degreeC in air | atmosphere by air in a reflow furnace, and formed the electrically conductive film. As a result of evaluating the obtained conductive film of Sample 11 in the same manner as in Example 1, the volume resistivity was 30.6 µΩ · cm, and the adhesiveness was 10 points of JIS evaluation scores.

Further, the glass substrate coated with the conductive composition of Sample 11 was heated and calcined at 190 ° C. for 20 minutes in an air atmosphere in a reflow furnace to form a conductive film of Sample 12. As a result of evaluating the obtained conductive film of Sample 12 in the same manner as in Example 1, the volume resistivity was 32.6 µΩ · cm, and the adhesion was 10 points of JIS evaluation scores.

In Examples 5 and 6, the conductive films of Samples 9 to 12 obtained while being fired at 200 ° C. or lower in an air atmosphere have a resistivity lower than 100 μΩ · cm, which is about 60 times that of bulk copper, and with a glass substrate. It turns out that adhesiveness is also favorable.

Example 7

17 parts by weight of copper powder [manufactured by Japan Atomize Co., Ltd., HXR-Cu] with an average particle diameter of 2.8 μm, 59 parts by weight of copper powder [Sumitomo Metal Mine Co., Ltd., UCP030] with an average particle diameter of 0.4 μm, 9 parts by weight of flat copper powder (Cu-HWF-6, manufactured by Fukuda Metal Powder Co., Ltd.) having an average particle diameter of 6.2 µm was mixed with 15 parts by weight of fine copper powder having an average particle diameter of 50 nm synthesized by a wet reduction method.

To 100 parts by weight of the obtained metal powder, 17 parts by weight of ethylene glycol as a solvent and 7 parts by weight of citric acid as an additive were added and mixed to adjust the conductive composition of Sample 13. This electrically conductive composition was apply | coated on the slide glass board | substrate by the method similar to the said Example 1, and heat-fired for 10 minutes at 300 degreeC in nitrogen atmosphere in the reflow furnace.

As a result of evaluating the electrically conductive film of the obtained sample 13 by the method similar to the said Example 1, volume resistivity was 5.21micro (ohm) * cm and adhesiveness was 10 points of JIS evaluation scores. In addition, in Example 7, since the heating and firing was short for 10 minutes, the resistivity of the conductive film of Sample 13 slightly increased, but it was found to be in a good range, and also excellent in adhesion to the glass substrate.

Example 8

In the said Example 2, the electrically conductive composition of the sample 14 was adjusted similarly except having changed the solvent into 15 weight part of diethylene glycol, and the electrically conductive film was formed on the slide glass substrate. As a result of evaluating the electrically conductive film of the obtained sample 14 by the method similar to the said Example 1, volume resistivity was 5.00 micrometer * cm and adhesiveness was 10 points of JIS evaluation scores.

In addition, in the said Example 2, the electrically conductive composition of the sample 15 was adjusted similarly except having changed the solvent into 15 weight part of glycerin, and the electrically conductive film was formed on the slide glass substrate. As a result of evaluating the electrically conductive film of the obtained sample 15 by the method similar to the said Example 1, the volume resistivity was 3.53micro (ohm) * cm and adhesiveness was JIS evaluation score 10.

According to Example 8, the conductive films of Samples 14 and 15 obtained had a very low resistivity of 5 μΩ · cm or less, which is about three times the resistivity of bulk copper by heating and baking at 300 ° C. for 60 minutes in an inert atmosphere of nitrogen. At the same time, adhesiveness with the glass substrate was also good.

According to the present invention, it is an inexpensive conductive composition using copper particles as a conductive filler, which can be fired at a low temperature not only in an inert atmosphere but also in an atmospheric atmosphere without a complicated process, and has excellent conductivity by preventing oxidation of the copper particles. The conductive composition which can form a conductive film can be provided.

Therefore, by using this conductive composition, 10 μΩ · cm or less of electric conductivity, which is about 6 times the resistivity of bulk copper, by firing at 300 ° C. or lower in an inert atmosphere without using reducing gas such as hydrogen gas with risk. By designing the film and suitable conditions, it is possible to form a conductive film of 5 μΩ · cm or less, which is about three times the resistivity of bulk copper. In addition, it is possible to form a conductive film of about 100 mu OMEGA -cm, which is about 60 times resistivity of bulk copper, by firing at 200 DEG C or lower in the atmospheric atmosphere.

Claims (10)

A conductive composition comprising a metal powder, a solvent, and an additive, wherein the metal powder is a mixture of copper powder having an average particle diameter of 0.3 to 20 µm and fine copper powder having an average particle diameter of 1 to 50 nm, wherein the solvent is an OH group. A polyhydric alcohol comprising two or more, wherein the additive is an organic acid having at least two COOH groups and at least one OH group, wherein the number of COOH groups is the same or more than the number of OH groups. The conductive composition of claim 1, wherein the metal powder is a mixture in which the fine copper powder is in a ratio of 1 to 100 parts by weight based on 100 parts by weight of the copper powder. The conductive composition according to claim 1 or 2, wherein the solvent is mixed at a ratio of 5 to 35 parts by weight based on 100 parts by weight of the metal powder. The conductive composition according to claim 1 or 2, wherein the additive is mixed at a ratio of 1 to 15 parts by weight with respect to 100 parts by weight of the metal powder. The conductive composition according to claim 1 or 2, wherein the solvent comprises at least one selected from ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and glycerin. The conductive composition according to claim 1 or 2, wherein the additive consists of at least one selected from malic acid, citric acid and tartaric acid. The electroconductive composition of Claim 1 or 2 containing a polar solvent with the said metal powder, a solvent, and an additive. The electrically conductive composition of Claim 1 or 2 is apply | coated on a board | substrate, and heat-processed, The formation method of the electrically conductive film characterized by the above-mentioned. 9. The method for forming a conductive film according to claim 8, wherein the method is calcined by heating at a temperature of 200 to 300 DEG C in an inert atmosphere. 9. The method for forming a conductive film according to claim 8, wherein the material is heat-fired at a temperature of 150 to 200 deg. C in an air atmosphere.